Deep oxidation of norfloxacin by the electrochemical enhanced heterogeneous catalytic oxidation: The role of electric field and reaction optimization

In this study, electrochemical (ECG-G: graphite anode and cathode, ECI-G: iron anode and graphite cathode) enhanced heterogeneous activation of peroxymonosulfate (PMS) by CoFe2O4 nanoparticles for the degradation of norfloxacin (NOR) in water was investigated. Although a higher NOR removal efficiency was achieved in ECI-G/CoFe2O4/PMS system, the generation of Fe3+ had resulted in the deposition of iron mud and affect the recovery of CoFe2O4. Under the optimum reaction conditions of CoFe2O4/PMS system, the final removal efficiency of NOR did not show significant difference in ECG-G/CoFe2O4/PMS system (96.0%) and CoFe2O4/PMS system (95.5%), but the value of apparent rate constant significantly increased in ECG-G/CoFe2O4/PMS system (0.21 min-1) compared with CoFe2O4/PMS system (0.11 min-1). Similar NOR degradation pathways were obtained in these two systems, and the TOC removal efficiency in ECG-G/CoFe2O4/PMS system (28.8%) is almost as low as CoFe2O4/PMS system (26.0%). Therefore, it can be proposed that the applied electric field through active electrodes can accelerate the reaction of heterogeneous catalytic oxidation, but does not participate much in NOR degradation. However, the TOC removal efficiency (30 min) could be reached 68.7% as the mass ratio of PMS to CoFe2O4 increased to 5:1 (250 mg L-1: 50 mg L-1). The ECG-G/CoFe2O4/PMS system is a promising low-cost technique for efficient mineralization of antibiotics in wastewater.